1. Field of the Invention
The present invention relates to a solar cell, and particularly relates to a solar cell with high light-absorbing efficiency and high optical-electrical converting efficiency, capable of lowering production cost and fabrication difficulty.
2. Description of Related Art
A solar cell has a very broad application spectrum appropriately covering electric power field (such as megawatts electric power generating system, home electric power generating system), communication field (such as wireless electric power, wireless communication), consumer electronic products (such as computer, watch, electric toy, radio receiver), traffic and transportation field (such as automobile, ship, traffic sign, road lighting, lighthouse), and agriculture field (such as water pump, irrigation).
Usually, a solar cell is formed by stacking a P-type semiconductor layer, an intrinsic semiconductor layer and an N-type semiconductor layer, wherein the materials of the P-type semiconductor layer, the intrinsic semiconductor layer and the N-type semiconductor layer are amorphous silicon. However, the intrinsic semiconductor layer made of amorphous silicon is disadvantageous in poor light-absorbing efficiency. A conventional method for solving this problem is to increase the thickness of the intrinsic semiconductor layer. However, as the thickness of the intrinsic semiconductor layer increases, the thickness of the solar cell is also increased, which raises the production cost thereof.
In addition to the above-mentioned method, another common method for enhancing light-absorbing efficiency is to repeatedly stack the P-type semiconductor layer, the intrinsic semiconductor layer and the N-type semiconductor layer to increase the number of layers. However, this method not only increases production cost and fabrication difficulty but increases internal resistance as well. Therefore, in this method, the P-type semiconductor layer, the intrinsic semiconductor layer, and the N-type semiconductor layer are not unrestrictedly stacked to achieve the purpose of increasing light-absorbing efficiency.